Electro-static charge is an undesired event and a major problem during the production of electronic components. Electro-static discharge (ESD) is vital to the manufacture of electronic components that are sensitive to static electricity, such as hard disk drives (HDD), semiconductors and electronic assemblies packaging. ESD may bring shorting-circuit, opening-circuit, loss of function, or disqualification of parameter to the electronic components, and thereby resulting in losing operational capability or performance reduction of them. ESD is regarded as the biggest potential killer to the quality of the electronic components, thus electro-static protection becomes a key content of controlling the quality of the electronic components.
Thus, ESD should be avoided or eliminated by static-control for electro-static protection for electronic components.
Typically, referring to FIG. 1, a disk drive unit 1′ contains a number of rotatable magnetic disks 15′ attached to a spindle motor 17′, and a head stack assembly (HSA) 13′ which is rotatable about an actuator arm axis for accessing data tracks on the magnetic disks 15′ during seeking. The HSA 13′ contains a set of drive arms 131′ and HGAs 132′ mounted on the ends of the drive arms 131′. Typically, a spindling voice-coil motor (VCM) 19′ is provided for controlling the motion of the drive arm 131′.
Referring to FIGS. 1 and 2, the HGA 132′ contains a magnetic head 12′ and a flexure 20′ supporting the magnetic head 12′. When the hard disk drive 1′ is on, the spindle motor 17′ will rotate the disk 15′ at a high speed, and the magnetic head 12′ will fly above the disk 15′ due to the air pressure drawn by the rotated disk 15′. The magnetic head 12′ moves across the surface of the disk 15′ in the radius direction under the control of the VCM 19′. With a different track, the magnetic head 12′ can read data from or write data to the disk 15′.
Generally, multiple electrical connection pads 134′ are arranged on one end of the flexure 20′ and adapted for connecting to the bonding pads of the magnetic head 12′ by the way of solder joints 148′. The other end of the flexure 20′ has a number of electrical pads 136′ (as shown in FIG. 3) disposed thereon and connected to a external control system (not shown). Thus, the flexure 20′ serves as the bridge electrically connecting the magnetic head 12′ and the external control system.
FIG. 3 shows a typical flexure configuration. Referring to FIG. 3, the flexure 20′ includes a stainless steel type (SST) layer 22′, a dielectric layer 24′, a copper layer 26′ and a Polyimide (PI) cover layer 28′. The detailed configuration of the flexure 20′ is that the dielectric layer 24′ is sandwiched between the SST layer 22′ and the copper layer 26′, and the PI cover layer 28′ covers the copper layer 26′. PI material as a plastic is a good electrical insulator, tending to acquire a strong electro-static charge which may result in ESD and cause damage and malfunction in the manufacturing or operational process of the flexure 20′. Because that the flexure 20′ is electrically connected to the magnetic head 12′, the ESD caused by the flexure 20′ also results in the damage of the magnetic head 12′, affects its function and performance.
In order to ensure the product security, the previous process of static-control for the flexure is dependent on dipping water. And the resistance of the flexure should be controlled at 105˜107 ohm to avoid ESD. However, the dipping water has some disadvantages. First, ultra-pure water used in the process of dipping water has high resistivity and is unstable for duration, the flexure may again generate static charges and damage itself. Second, water is easy to breed bacteria, harmful to the health of employees or consumers. Third, water may erode the components, which reduces the lifetime of the flexure. In addition, the method of dipping water for preventing ESD takes effect only in the manufacturing process, but can not work in the operational process when the flexure has been mounted on the HDD.
Hence, it is desired to provide a flexure, an HGA, and a disk drive unit to overcome the above-mentioned drawbacks.